1. Field of the Invention
The present invention generally relates to apparatus and methods employed in conjunction with crossing guard mechanisms. The present invention more particularly relates to use of mechanical and electrical means to enable the safe repair of a crossing guard mechanism, such as a mechanism employed at a railroad crossing.
2. Background Information
It has been known to position crossing guard mechanisms adjacent to certain designated areas to resist the passage of pedestrians, drivers and other individuals into those areas. A crossing guard mechanism positioned adjacent to a locomotive crossing, for example, hinders the unsafe passage of individuals over the railroad tracks when arrival of a train is imminent. Unfortunately, a common problem arises with a crossing guard mechanism when its guard arm is struck by a vehicle, for example, or another disturbance affects the mechanism and the guard arm becomes detached from the mechanism. This event can also adversely affect the control and operating circuitry of the crossing guard mechanism. An example of a highway crossing gate control circuit is provided by U.S. Pat. No. 5,502,367 to Jones, which is incorporated herein in its entirety by reference.
A complication created by this situation is how to move a counterweight arm of the crossing guard mechanism to its "up" or horizontal position in a safe and efficient manner. The counterweight arm is normally employed in a crossing guard mechanism to counterbalance the weight of the guard arm at a common connection point between the two arms. The common connection point provides the mechanical advantage needed to permit the guard arm to be raised and lowered as required. To repair a disabled crossing guard mechanism, the guard arm connection point must be lowered to an accessible position or its "down" position. A connection point on the counterweight arm can then be aligned with a connection point on the guard arm to permit reconnection of the guard arm to the guard mechanism.
Difficulty arises in this situation from the weight of the counterweight arm. The weight of this counterweight arm is proportional to the length of the guard arm and is substantial. The crossing guard system generally becomes unbalanced and disrupted as a result of the unexpected removal of the guard arm. Once the system is unbalanced, substantial mechanical advantage is required to raise the counterweight arm. Furthermore, the operator must be able to raise the counterweight arm in a manner which does not substantially jeopardize his safety and which protects the crossing guard equipment, including its control circuitry, in the event of loss of electrical power to the mechanism while moving the counterweight arm or arms to the "up" position. Without taking protective measures, the counterweight arm can fall in a relatively rapid and uncontrolled manner, possibly endangering the operator and/or causing damage to the crossing guard mechanism.
Maintenance systems have been implemented within crossing guard mechanisms, but these systems generally utilize relatively expensive relays and a number of different components. Many maintenance systems are included within and connected to the normal control and operating circuitry of the crossing guard mechanism. This interdependence between the maintenance system and the usual crossing guard functions inherently lowers the reliability of the normal function of the mechanism.
What is needed therefore are a maintenance system and an associated method which provide safety and reliability advantages that are not obtainable in other designs that rely on a constant source of electrical power to engage relatively complex components such as electromechanical brakes or relays, for example. What is also needed are a maintenance system and an associated method that can be performed simply and reliably to service a crossing guard mechanism. Furthermore, a maintenance system and method are needed that are substantially independent from the operation of the electrical control and operation circuitry of the crossing guard system.